1. Field of the Invention
The present invention relates to a main pole excitation type magnetic head for vertical recording and process for producing the same.
2. Description of the Prior Art
A conventional mainpole excitation type magnetic head for vertical magnetic recording (hereinafter to be referred to as magnetic head) is of the structure as shown in FIGS. 1 (a) and (b), in which FIG. 1 (a) is a perspective view showing the magnetic head and FIG. 1 (b) is an exploded perspective view of the magnetic head. Referring to the drawings, 1 denotes a slider subassembly on the recording and reproducing side, which is formed of a slider member 2 made of ceramic, nonmagnetic ferrite, or the like and provided with a coil groove 2a and a protrusion 2b and a magnetic core 3 made of magnetic material such as ferrite in a substantially flat plate form, disposed on the side of the coil groove 2a of the slider member 2, and put in close contact with the inner side 2c of the protrusion 2b and fixed thereto with resin, fusion glass, or the like. On the flat portion formed of the protrusion 2b of the slider member 2 and the surface 3a of the magnetic core 3 not in contact with the slider member 2, there is provided magnetic thin film 4 for recording and reproducing formed from cobalt amorphous, permalloy series, or sendust series magnetic material by a method such as sputtering, evaporation, or the like.
Symmetrically with the slider subassembly on the recording and reproducing side, there is provided a slider subassembly 5 on the erasing side, which is formed of a slider member 6 made of ceramic, nonmagnetic ferrite, or the like and provided with a coil groove 6a and a protrusion 6b, and a magnetic core 7 made of magnetic material such as ferrite in a substantially flat plate form, disposed on the side of the coil groove 6a of the slide member 6, and put in close contact with the inner side 6c of the protrusion 6b and fixed thereto with resin, fusion glass, or the like. On the flat portion formed of the protrusion 6b of the slider member 6 and the surface 7a of the magnetic core 7 not in contact with the slider member, there is provided magnetic thin film 8 for erasing formed from cobalt amorphous, permalloy series, or sendust series magnetic material by a method such as sputtering, evaporation, or the like.
Numeral reference 9 denotes a center slider member, which is provided with coil grooves 9a, 9b at the positions opposite to the coil grooves 2a, 6a of the slider members 2, 6.
In constructing the magnetic head, the slider subassembly 1, the center slider member 9, and the slider subassembly 5 are assembled, when relative positioning of the magnetic thin film 4 and the magnetic thin film 8, 8 is made so that, as shown in FIG. 2, the effective record width 13 recorded by the magnetic thin film 4 may be erased by the magnetic thin film 8, 8 to a specified record width 14, and then these members are fixed together with adhesive, resin, fusion glass, or the like 10. Incidentally, the arrow 15 in FIG. 2 indicates the direction of the movement of a magnetic recording medium (not shown).
Thereafter, a recording and reproducing winding 11 and an erasing winding 12 are provided for the assembly and its sliding surface for sliding along the magnetic recording medium (not shown) is ground or lapped and the magnetic head is thus completed.
In the above described process, the magnetic thin film 4, 8 must be applied to the surface formed of the protrusions 2b, 6b and the sides 3a, 7a of the magnetic cores 3, 7 not in contact with the slider members 2, 6 being finished to an even surface after the magnetic cores 3, 7 have been put in close contact with the inner sides 2c, 6c of the protrusions 2b, 6b of the slider members 2, 6 and fixed thereto. Otherwise, gaps would be formed between the inner sides 2c, 6c of the protrusions 2b, 6b of the slider members 2, 6 and the cores 3, 7 thereby to split the magnetic film 4, 8 at the joined portion of the slider members 2, 6 and the magnetic cores 3, 7 and the magnetic circuit would thereby be broken. The same trouble would occur if there were formed differences in level between the slider members 2, 6 and the magnetic cores 3, 7.
To prevent such trouble, the protrusions 2b, 6b of the slider members 2, 6 and the sides 3a, 7a of the magnetic cores 3, 7 must be finished to even common surfaces. Further, the magnetic thin film 4, 8 must be correctly positioned relative to each other after the slider subassembly 1, the center slider member 9, and the slider subassembly 5 have been assembled, and, after the positioning has been made, the three members, namely, the slider subassembly 1, the denter slider 9, and the slider subassembly 5 must be fixed together. Such being the case, a considerably long time is taken for the positioning, the workability is lowered very much, and, in addition, the task for attaining the accurate positioning is so difficult that skilled workers are needed therefor. Furthermore, since the slider subassembly 1, the center slider member 9, and the slider subassembly 5 must be assembled and fixed together, the sliding surface of the magnetic head along the magnetic recording medium, or more specifically (refer to FIG. 1 (a), the top surfaces 2d of the slider subassembly 1, 9c of the center slider member 9, and 6d of the slider subassembly 5 are liable to produce differences in level therebetween. Hence, a grinding process becomes necessary to remove such differences in level and provide an even common surface. As to the winding work to provide windings 11, 12 (FIG. 1 (b)), since thin wires must be inserted into the thin winding holes formed by the center slider member 9 and the slider members 2, 6 and wound into coils, the workability is kept very low, breakage of the wire is liable to occur and man-hours for the winding become larger. Besides, since a winding machine cannot be utilized for such winding work, skill is required of the winding workers.
According to the structure of the prior art magnetic head, the coil grooves 9a, 9b are disposed on the center slider member 9. Since these coil grooves 9a, 9b must be provided there, when it is attempted to shorten the distance between the magnetic thin film 4 and the magnetic thin film 8, 8, there is a certain limit in the attainable distance. Therefore, when it is intended to make high-density recording on a magnetic medium of a smaller radius of curvature, 3 or 3.5 inches in diameter, for example, a certain restriction will be found in carrying out the intention. The situation will be described below in more detail. In the case where the distance between the center of rotation of a magnetic medium and a magnetic head is smaller, or, in other words, when the magnetic recording medium is smaller in diameter or it is attempted to take magnetic recording closer to the center, the magnetic recording medium rotates in a small-diametered circular arc C with reference to the magnetic head H. Then, if the distance 1 between the magnetic thin film 4 and 8 is larger, the positions to be erased by the erasing magnetic thin film 8, 8 at both ends of the effective record width W recorded by the recording and reproducing magnetic thin film 4 will deviate from the right positions to be erased. For this reason, there have been such problems that it is unable to make record in a smaller-diametered magnetic recording medium or a magnetic recording medium cannot be effectively utilized inward to the smaller-diametered portion.
Furthermore, since the erasing coil must be provided by winding a wire across the entire length of the erasing magnetic core, the produced magnetic flux leaks out to unnecessary portions, or a large amount of so-called leakage flux is produced, and the erasing current efficiency is thereby lowered. The workability is also lowered because the winding must be made manually and the manufacturing cost becomes higher because a larger amount of wire material is needed for the coil.
In addition, it has come to be known that the magnetic field produced by the erasing current flowing through the erasing coil may adversely affect the magnetic recording by the recording signal current flowing through the recording and reproducing coil. That is, the erasing magnetic field produced by the erasing current may be turned out to be leakage flux coming into the core block on the recording and reproducing side, and the recording magnetic field produced by the recording and reproducing coil may thereby be disturbed, and desired signal may become unable to be recorded in the recording medium. Due to the leakage of the erasing magnetic field, there also arises a problem that the erasing efficency is worsened.